Double S-scheme AgBr heterojunction co-modified with g-C3N4 and black phosphorus nanosheets greatly improves the photocatalytic activity and stability

Synergic action of bamboo-cellulose-supported hydrogen-bonded nano-AgBr for robust photocatalysis

A novel semiconductor photocatalyst was developed using bamboo cellulose fibers (BCFs) embedded with nano-AgBr (AgBr@BCFs) via a simple and rapid method. BCFs prevented the agglomeration of AgBr and provided numerous active reaction sites as a dispersant and structural support. The photocatalytic activity of AgBr@BCFs in removing organic pollutants was investigated and the endogenous factors leading to the high activity were analyzed through a combination of a series of experiments, characterizations and theoretical calculations. We propose that the efficient photocatalytic performance of AgBr@BCFs was attributed to the interface integration facilitated by hydrogen bonds and robust electronic interactions. The interface demonstrated a significantly negative reduction potential (-0.57 eV), enhancing carrier transport efficiency and inhibiting the recombination of photogenerated electron-hole pairs. Compared to the intrinsic activity of AgBr, AgBr@BCFs exhibits 7.2 times higher performance for Rhodamine B and 8.6 times greater intensity for tetracycline (TC). Additionally, the applicability of the photocatalyst across various pH ranges, photocorrosion resistance, and recyclability were evaluated. The mechanism of the photocatalytic process revealed that the synergistic bifunctionality of high adsorption rate and strong degradation activity is the primary reason for the high activity. BCFs-based semiconductor material can be recycled efficiently, which is a promising photocatalyst for the purification of organic sewage.

ZnO/black phosphorus/C3N4 composite: An effective photocatalyst for Cr (VI) reduction and degradation of rhodamine B

The utilization of photocatalysts offers a promising approach for the removal of Cr (VI) and rhodamine dyes. Through the generation of reactive species and subsequent degradation reactions, photocatalysis provides an efficient and environmentally friendly method for the remediation of wastewater. In this study, we have synthesized an n-p-n heterojunction of carbon nitride (C3N4), zinc oxide (ZnO), and black phosphorus (BP) through the sonication-stirring method. The photocatalytic ability of this composite was examined for the decomposition rhodamine B (RhB) and detoxification of hexavalent chromium ion (up to 97% during 80 min) under Xenon irradiation. The results of trapper experiments indicated that the active species were hydroxyl radical (˙OH), electron (e-), and superoxide anion radical (˙O2-). Based on the obtained potential of the lowest unoccupied molecular orbitals (LUMO) and the highest occupied molecular orbital (HOMO) for the mentioned semiconductors, through Mutt-Schottky results, the double Z-scheme mechanism was proposed for the studied process. The electrochemical impedance spectroscopy data exhibited good charge transfer for the evaluated composite versus the pure compounds. The impressive separation of holes and electrons along with the low recombination were confirmed by the responses of photocurrent and quenching the photoluminescence (pl) intensity for the composite, respectively. The current density of the composite recorded 66.6%, 87.3%, and 92% higher than those of BP, C3N4, and ZnO, indicating an excellent electron-hole separation for the ternary composite compared to the pure semiconductors. Diffuse reflectance spectra (DRS) data revealed 2.9, 3.17, 1.15, and 2.63 eV as the band gap values for C3N4, ZnO, BP, and composite. The rate constant of the new composite to remove RhB and reduce hexavalent chromium were about 4.79 and 2.64 times higher than that of C3N4, respectively.

An S-scheme NH2-MIL-101(Fe)@MCN/Bi2O3 heterojunction photocatalyst for the degradation of tetracycline and production of H2O2

Effective and durable photocatalysts are essential for the decomposition of persistent contaminants and the generation of hydrogen peroxide. In this study, we successfully constructed an S-type heterojunction by in situ growing Bi2O3 nanocrystals and NH2-MIL-101(Fe) onto surface-modified g-C3N4. The process of charge transfer in the S-type heterojunction was confirmed using ISI-XPS, DFT calculations, capture experiments, and EPR signals. The combined influence of the heterojunction and MOF demonstrated remarkable photocatalytic performance in the breakdown of tetracycline (TC) and the generation of hydrogen peroxide (H2O2). In the enhanced setup (10%-NH2-MIL-101(Fe)@MCN/Bi2O3), full degradation of TC was accomplished within 50 min under visible light exposure. Additionally, a notable H2O2 yield of 655.63 μmol/g was attained, all achieved without the necessity of sacrificial agents or supplementary oxygen. Based on the outcomes of the dual functionality, the exceptional performance of the ternary composite material can be ascribed to the collaborative influence of the heterojunction and MOF. This collaborative effect expands the light absorption range in the visible region, suppresses the recombination of electron-hole pairs, and enhances the photocatalytic redox ability. The system demonstrates significant potential in the efficient in situ production of H2O2 and removal of recalcitrant organic pollutants in pure water.

AgBr nanoparticle surface modified SnO2 enhanced visible light catalytic performance: characterization, mechanism and kinetics study

In this study, a simple hydrothermal procedure and in situ precipitation method were used to prepare SnO2-AgBr composites, where the molar ratios of SnO2 and AgBr were 1 : 1, 1 : 2 and 2 : 1. Characterization results showed that the composites had excellent dispersion, crystallinity, and purity. A photocatalytic degradation experiment and first-order kinetic model indicate that SnO2-AgBr (1 : 1) had the best photocatalytic performance, and the degradation rates of 30 mg L-1 simulated MO and MG wastewater reached 96.71% and 93.36%, respectively, in 150 min, which were 3.5 times those of SnO2. The degradation rate of MO and MG increases with the dosage. Humic acid inhibited the degradation of MG, while a low concentration of humic acid promoted the degradation of MO, and the composite has good stability with pH. A free radical trapping experiment shows that ·OH and ·O2- were the main active substances, and h+ was the secondary one. According to the results of the characterization and photocatalysis experiments, a Z-scheme mechanism for the SnO2-AgBr composite was proposed, and the degradation pathway of target pollutants was speculated upon. This study has conceived novel methods for the development of a mature Z-scheme mechanism and in doing so has provided new approaches for the development of photocatalysis for water pollution control.

Black Phosphorus-Doped Graphitic Carbon Nitride with Aromatic Benzene Rings for Efficient Photocatalytic Hydrogen Production

Graphitic carbon nitride (g-C3N4, abbreviated as g-CN) suffers from low visible-light-responsive photocatalytic efficiency. In this study, aromatic benzene rings and black phosphorus (BP) were successfully incorporated into g-CN photocatalysts (BP/A-CN), resulting in modified materials with improved properties. Structural analysis confirmed the successful integration of aromatic rings and BP into the g-CN framework, indicating the formation of a stable composite. Morphological characterization revealed that the introduction of aromatic rings and BP did not cause any significant changes in the nanosheet-like morphology of the g-CN photocatalysts. To evaluate the photocatalytic hydrogen production activity under visible-light irradiation, various compositions of aromatic benzene rings and BP were investigated. Specifically, the BP/A-CN composite exhibited an enhanced photocatalytic hydrogen production rate (860 μmol g-1 h-1), which was approximately 4.0 times higher than that of g-CN (210 μmol g-1 h-1). The improved hydrogen production rates observed in the modified g-CN photocatalysts can be attributed to several factors. First, the aromatic benzene rings and BP enhanced light absorption, thereby improving the efficient utilization of solar energy. Additionally, the presence of these components in the composite photocatalysts reduced electron-hole recombination, thereby facilitating improved charge transfer and separation efficiencies. Overall, this study demonstrates the potential of incorporating aromatic benzene rings and BP into g-CN photocatalysts for efficient solar energy conversion. These findings contribute to the development of novel photocatalytic materials with enhanced performance and highlight the versatility of g-CN-based composites for various applications in environmental and energy fields.

Construction of a novel double S-scheme structure WO3/g-C3N4/BiOI: Enhanced photocatalytic performance for antibacterial activity

In recent years, the threat to human health from bacteria in wastewater has attracted attention, and photocatalytic technology has emerged as a promising strategy for inactivating bacteria in water. Therefore, it is of great research value to develop a novel high-efficiency photocatalytic system with the visible light response. We successfully designed a double S-scheme heterojunction composite WO₃/g-C₃N₄/BiOI (WCB) in this paper. The preparation of WCB composites was demonstrated by a series of characterizations, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM). The antibacterial effects of photocatalysts against representative Gram-negative strain Escherichia coli (E. coli) and Gram-positive strain Staphylococcus aureus (S. aureus) were tested under LED light irradiation. The novel photocatalyst presented excellent antibacterial properties, inactivating E. coli in 12 min and S. aureus in 20 min. The bacterial cell inactivation process was studied by scanning electron microscopy (SEM) and Confocal Laser Scanning Microscopy (CLSM). Active species capture experiments show that the active species present in the WCB composites in the process of inactivating bacteria are h⁺, e^-, OH and O₂^-. In conclusion, the synthesized double S-scheme WCB photocatalyst exhibits remarkable photocatalytic antibacterial activity under LED light and has broad prospects for practical application in water antibacterial treatment.

Nanomaterials-Based Ion-Imprinted Electrochemical Sensors for Heavy Metal Ions Detection: A Review

Heavy metal ions (HMIs) pose a serious threat to the environment and human body because they are toxic and non-biodegradable and widely exist in environmental ecosystems. It is necessary to develop a rapid, sensitive and convenient method for HMIs detection to provide a strong guarantee for ecology and human health. Ion-imprinted electrochemical sensors (IIECSs) based on nanomaterials have been regarded as an excellent technology because of the good selectivity, the advantages of fast detection speed, low cost, and portability. Electrode surfaces modified with nanomaterials can obtain excellent nano-effects, such as size effect, macroscopic quantum tunneling effect and surface effect, which greatly improve its surface area and conductivity, so as to improve the detection sensitivity and reduce the detection limit of the sensor. Hence, the present review focused on the fundamentals and the synthetic strategies of ion-imprinted polymers (IIPs) and IIECSs for HMIs detection, as well as the applications of various nanomaterials as modifiers and sensitizers in the construction of HMIIECSs and the influence on the sensing performance of the fabricated sensors. Finally, the potential challenges and outlook on the future development of the HMIIECSs technology were also highlighted. By means of the points presented in this review, we hope to provide some help in further developing the preparation methods of high-performance HMIIECSs and expanding their potential applications.

Preparation and Application of Electrochemical Horseradish Peroxidase Sensor Based on a Black Phosphorene and Single-Walled Carbon Nanotubes Nanocomposite

To design a new electrochemical horseradish peroxidase (HRP) biosensor with excellent analytical performance, black phosphorene (BP) nanosheets and single-walled carbon nanotubes (SWCNTs) nanocomposites were used as the modifier, with a carbon ionic liquid electrode (CILE) as the substrate electrode. The SWCNTs-BP nanocomposite was synthesized by a simple in situ mixing procedure and modified on the CILE surface by the direct casting method. Then HRP was immobilized on the modified electrode with Nafion film. The electrocatalysis of this electrochemical HRP biosensor to various targets was further explored. Experimental results indicated that the direct electrochemistry of HRP was realized with a pair of symmetric and quasi-reversible redox peaks appeared, which was due to the presence of SWCNTs-BP on the surface of CILE, exhibiting synergistic effects with high electrical conductivity and good biocompatibility. Excellent electrocatalytic activity to trichloroacetic acid (TCA), sodium nitrite (NaNO₂), and hydrogen peroxide (H₂O₂) were realized, with a wide linear range and a low detection limit. Different real samples, such as a medical facial peel solution, the soak water of pickled vegetables, and a 3% H₂O₂ disinfectant, were further analyzed, with satisfactory results, further proving the potential practical applications for the electrochemical biosensor.

Facile assembly and excellent elimination behavior of porous BiOBr-g-C3N4 heterojunctions for organic pollutants

Photocatalysis can be an effective technique for eliminating organic contaminants from water. In this study, BiOBr flower-spheres coupled with porous graphite carbon nitride (g-C₃N₄) were synthesized by controlling the dosage of cetyltrimethylammonium bromide (CTAB). Various characterization techniques were then applied to elucidate the structure-performance relationships of the resulting heterojunction photocatalysts in degrading organic dyes. Experimental results established an optimal molar ratio for KBr to CTAB of 5:1. Benefiting from a remarkable porous structure and tight coupling between porous g-C₃N₄ and BiOBr, the optimal BiOBr-g-C₃N₄(2%) exhibited enhanced visible light absorption capability and promoted the separation of photoinduced carriers. Total removal efficiency for rhodamine B (RhB, 25.0 mL, 20.0 mg L^-1) reached 87% within 30 min in the presence of BiOBr-g-C₃N₄(2%) (20.0 mg) (i.e., 1.51 μmol (g_{photocatalyst} min)^-1), which is superior to the performance of BiOBr (72%) (i.e., 1.25 μmol (g_{photocatalyst} min)^-1), g-C₃N₄ (21%) (i.e., 0.37 μmol (g_{photocatalyst} min)^-1). Furthermore, the photocatalytic reaction rate constant over the optimal heterojunction was 0.034 min^-1, which is significantly larger than those of porous g-C3N4 (0.003 min^-1) and BiOBr (0.015 min^-1). Moreover, this type II heterojunction showed good universality for other organic dyes (such as methyl violet, methylene blue, and crystal violet), highlighting a promising potential role in the elimination of environmental pollutants.